138 PEOFESSOll E. RAT LANKESTER. 



found forming the cortical or outer layer of the entapophysial 

 ligament — a stronar band which connects the successive dorsal 

 entapophyses with one another. It also, in a modified form, 

 constitutes the tendons of the branchio thoracic muscles (PI. 

 IX, fig. 4.) For figures and an account of the relations of 

 these parts I must refer the reader to my paper above mentioned, 

 on the muscular and skeletal system of Limulus and Scorpio. 



Histology of the Entosternite of the Scorpion. — 

 The entosternite of the Scorpion is composed of a tissue 

 very closely similar to that just described. The cells are 

 somewhat smaller in size, and more constantly disposed in 

 elongated groups, two — eight or more placed in a row — in 

 what may be called '^ fissures ^^ of the dense but slightly fibril- 

 lated matrix. As in the case of the Limulus entosternite, so 

 here the tissue appears to yield no gelatin nor chondrin, but 

 chitin and mucin. The staining with Borax carmine is taken 

 up in the same way as in Limulus, viz. hardly at all by the cell 

 protoplasm but strongly by the matrix and the nuclei. 



In PI. VII, fig. 1, a piece of the entosternite of Androc- 

 tonus funestus, Ehr., is drawn, showing, as well as the cha- 

 racteristic tissue, the insertion of muscular fibres into it by 

 means of the continuity of the inter-muscular connective tissue 

 with the tissue of the entosternite. In the upper part of the 

 figure is also shown the continuity of the fibroid tissue of the 

 entosternite with the characteristic '^ lacunar connective tissue,'^ 

 which forms so large a part of the packing of the viscera in 

 Scorpio and Limulus, and is especially richly developed between 

 the cseca of the great gastric gland or so-called "liver" (see 

 below). 



In Scorpio I have found the fibroid tissue of the entosternite 

 developed only in one other region, namely, in a small tendi- 

 nous plate overlying the base of the pectines — modified appen- 

 dages corresponding to the first pair of branchial appendages of 

 Limulus. This plate corresponds in position and muscular 

 connection, as in structure, with one of the small entosternites 

 of the mesosoma of Limulus. 



My gale. — The fibro-massive tissue of the entosternite of 



